It is known to construct a roof of a plurality of overlapped tiles, such as clay tiles. This type of tile is quite expensive to apply because of its weight and the methods required for installation. The use of plastic tiles for roofing or for siding is known, plastic being generally less expensive because of its light weight and ease of installation.
It is also known to provide a panel with interlocking parts to secure adjacent panels together. One such interlocking panel is shown in U.S. Pat. No. 3,289,375 (Cline). This patent teaches a flat panel having a web extending from the bottom surface of a flange and terminating in a fork-like connecting part. The fork engages L-shaped hooks on edges of two facing panels to secure the three panels together. The structure shown by the Cline patent would be extremely difficult to assemble and would not be effective with plastic materials because of their high coefficients of thermal expansion. More importantly, Cline's structure does not permit the overlapping required for roofing tile.
Other interconnecting panels used in building construction are shown in U.S. Pat. No. 3,191,724 (Ridder) and U.S. Pat. Re. No. 626,006 (Heidt).